Margaret Woodley-Krug, right, and her mother, Marie Cunningham, at their home in Waldorf, Md. Woodley-Krug, 65, is participating in a trial of a drug designed to prevent the onset of Alzheimer's Disease. Cunningham, 86, suffers from dementia. (Andre Chung for The Washington Post)

Last month, I wrote about the problems that pharmaceutical companies and other researchers have recruiting sufficient numbers of volunteers for clinical trials of medications that may prove valuable against a wide variety of disorders. Here is one example of how that may affect people who might benefit from that research. -- Lenny Bernstein.

`A large and potentially groundbreaking drug trial holds the promise of a new way to treat Alzheimer's disease, but the test will require thousands of healthy volunteers who may be especially difficult to recruit, in part because of a simple fact about the widely feared illness: Those who have, or are likely to get, Alzheimer's disease may not want to know it.

The Anti-Amyloid Treatment in Asymptomatic Alzheimer's, or A4 Study, is the first to try to prevent memory loss by identifying and treating people whose brains show the earliest changes related to the disease, years before they begin to lose cognitive function.

Volunteers aged 65 to 85 will be screened for the presence of amyloid plaque, clumps of a protein found in the fatty membrane surrounding nerve cells, that builds up in the brain as people age and seems to be connected to Alzheimer's. Researchers hope the drug could significantly curtail the disease, which currently afflicts 5 million Americans and is projected to affect 16 million by 2050.

Over the past two months, researchers at 60 sites across the U.S., Canada and Australia began seeking as many as 10,000 volunteers to be screened for the 39-month trial, which is sponsored by the National Institutes of Health, the pharmaceutical company Ely Lilly & Co., and others.

"Everyone's putting their bets on this horse," said Scott Turner, director of the Memory Disorders Program at Georgetown University, one of the participating sites.

[For information on how to volunteer for the study, see the end of this post.]

By September, all 60 sites will be screening volunteers until 1,000 are found who are eligible. But several sites have expressed concern about being able to find enough volunteers. So far, 500 people have expressed interest nationally and 50 are in the screening process.

Despite intensive recruiting, just five people have been scheduled for screening at Turner's site and only one has begun it. "We're worried that we're not going to be able to recruit at the rate we're hoping to," Turner said. "People may not want to know, because there are just not good treatments out there now."

Research is increasingly focusing on halting the debilitating symptoms of Alzheimer's before they begin, said Kevin Keith Fargo, director of scientific programs and outreach at the Alzheimer's Association.

"This is becoming a very active area of research, to look earlier in the disease process," he said. "We're trying to get to the ... place with Alzheimer's where we don't wait for the onset of dementia."

The A4 Study's requirements set a particularly high bar for volunteers. Those who have the plaque buildup must pass health and cognitive tests to qualify. The screening also includes efforts to ensure that participants are psychologically prepared to receive the news that they have amyloid buildup.

An estimated one third of volunteers are expected to have enough buildup to qualify for the trial. Half of the 1,000 who enroll will receive a placebo and half will receive the drug solanezumab, which researchers hope will flush out the amyloid before it can build up enough to cause cognitive problems. If it is shown to be effective, all participants will be given the drug at the end of the trial.

Solanezumab was not effective in earlier trials involving people who already had full-blown Alzheimer's disease, but it did have promising effects on the mildest cases, leading researchers to believe it could work at pre-symptomatic stages.

“I think if this trial works, it really will shift the way we think about Alzheimer’s research,” making it more like HIV, diabetes, heart disease and other diseases that can be prevented before they become catastrophic, said Reisa Sperling, a Harvard Medical School neurology professor who is leading the trial.

The trial has another significant recruiting challenge: Sperling is insisting that at least one fifth of participants come from underrepresented groups such as African Americans and Latinos, who generally make up only 5 percent of clinical trials.

"I've gotten a lot of pushback from sites saying, 'We can recruit but we're not sure we can get you that one-fifth,' " she said.

If a site is not able to come up with enough diversity among its recruits, she said, it may be put on hold. Recruiters are turning to churches and universities with large minority populations to spread the word.

More studies on pre-symptomatic people are expected, but they, too, may have a difficult time recruiting people, said Laurie Ryan, director of the Alzheimer's disease clinical trials program at the National Institutes of Health. Ryan said she hopes those who have seen the disease up close will be moved to volunteer.

Margaret Woodley-Krug, 65, a school librarian in Waldorf, Md., volunteered to be screened at Georgetown because her mother, who lives with her, has dementia. Participating would make her feel she was doing some good for others, perhaps even for her own children, Woodley-Krug said.

"Personally I'm the type of person that, if I have the possibility, I would rather know so I can prepare," she said.

Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.

To pause and restart automatic updates, click "Live" or "Paused". If paused, you'll be notified of the number of additional comments that have come in.

Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.